Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
Item Características hidráulicas e fotossintéticas em espécies C3 e C4 proximamente relacionadas(Universidade Federal de Viçosa, 2023-08-01) Castro, Carolina Souza de; Martins, Samuel Cordeiro Vitor; http://lattes.cnpq.br/2674257594803408As plantas C4 são conhecidas por manter uma alta eficiência fotossintética e maior eficiência do uso da água em relação às espécies C3. No entanto, pouco se sabe sobre as diferenças nas relações hídricas entre os tipos fotossintéticos, principalmente em espécies pertencentes a grupos de transição entre os tipos C3 e C4. Este trabalho teve como objetivo explorar as características hidráulicas, anatômicas e fotossintéticas em espécies C3 (Tarenaya hassleriana (Th) e T. longicarpa (Tl)) e C4 (Gynandropsis gynandra (Gg)) relacionadas da família Cleomaceae. Nos parâmetros de relações hídricas, o teor relativo de água no ponto de perda de turgescência foi similar nas três espécies (0,89). As espécies Th e Gg apresentaram valores similares para o potencial osmótico em turgescência plena (-0,80 MPa), potencial hídrico no ponto de perda de turgor (-0,84 MPa) e na capacitância pré-perda de turgor (C PT , 1,30 mol m -2 MPa -1 ); no entanto, a C4 apresentou uma alta C PPT (6,28 mol m -2 MPa -1 ). As espécies Tl e Gg apresentaram taxas fotossintéticas semelhantes (22,35 µmol CO 2 m - s -1 ), porém a espécie C4 apresentou a menor razão entre a taxa de transporte de elétrons pela taxa fotossintética (5,95). Em relação à condutância hidráulica foliar, as três espécies obtiveram valores semelhantes. Por outro lado, as espécies C3 foram mais vulneráveis à cavitação do que a espécie C4, sendo que esta última apresentou a maior margem de segurança hidráulica. Com isso, a espécie C4 pode ser considerada como uma planta eficiente e segura do ponto de vista hidráulico, sugerindo que tal vantagem pode ter sido chave para a evolução em ambientes áridos. Palavras-chave: Eficiência hidráulica. Vulnerabilidade hidráulica. Eficiência do uso da água. Cleomaceae.Item Efeitos interativos da concentração de CO 2 e da disponibilidade de luz sobre o crescimento, o desempenho fotossintético e a plasticidade fenotípica do cafeeiro(Universidade Federal de Viçosa, 2022-02-23) Souza, Antonio Henrique de; Matta, Fábio Murilo Da; http://lattes.cnpq.br/9279364211711324Apesar de o café arábica (Coffea arabica L.) ser uma espécie que evoluiu em ambientes sombreados, é cultivado, mais comumente, a pleno sol, como ocorre no Brasil. A espécie é classificada como muito sensível às mudanças climáticas, e o uso do sombreamento em cafezais é considerado uma importante estratégia de manejo para mitigar os efeitos negativos dessas mudanças, de sorte que a adoção do sombreamento em lavouras a pleno sol é assunto atual de destaque na cafeicultura. A cultura apresenta grande plasticidade fenotípica à irradiância, observada quando há diferenças marcantes na disponibilidade de luz. A elevada concentração atmosférica de CO 2 (eC a ) aumenta o desempenho fotossintético do cafeeiro, porém, ainda não se sabe se, e como, a eC a pode afetar o desempenho fotossintético do cafeeiro sob sombreamento mais denso e se a eC a poderia reverter as limitações difusionais impostas às plantas de café nessa condição, quando sua plasticidade fenotípica à luz é induzida. Isso posto, pretendeu-se avaliar como a assimilação e o uso de carbono, bem como o acúmulo e partição de biomassa, são afetados pela disponibilidade de luz e concentração de CO 2 , e como isso poderia impactar a plasticidade fenotípica do cafeeiro à irradiância. Para tanto, foram cultivadas plantas em vasos, dentro de câmaras de topo aberto, em casa de vegetação. Durante 12 meses, as plantas foram submetidas a dois níveis de luz (0% e 90% de restrição lumínica) em combinação com concentração de CO 2 ambiente (aC a : 457 ± 9 µmol mol -1 ) ou elevada (eC a : 705 ± 18 µmol mol -1 ). Foram realizadas avaliações de trocas gasosas e fluorescência de clorofila a, curvas fotossintéticas de resposta à concentração interna de CO 2 (A/C i ), partição e eficiência de uso de nitrogênio, além de análises bioquímicas, anatômicas e biométricas. Os resultados demonstraram que eC a melhorou a performance fotossintética, via aumentos na taxa fotossintética líquida (A) e redução da taxa de fotorrespiração e da pressão oxidativa nos cloroplastos, sem sinais de retrorregulação da fotossíntese. Por um lado, o incremento em C a atenuou os efeitos das limitações difusionais exacerbadas pelo drástico sombreamento, além de aumentar a velocidade máxima de carboxilação da RuBisCO (V cmax ), em paralelo a aumentos na eficiência fotossintética do uso do N, mas sem efeito direto na condutância estomática (g s ) e condutância mesofílica dessas plantas. Em adição, houve maior uso fotoquímico da luz absorvida sob condições de sombra (maior coeficiente de extinção fotoquímico e maioreficiência fotoquímica atual do FSII), em paralelo com maiores concentrações de clorofila e maior investimento em N como um todo na maquinaria fotossintética. Por outro lado, as plantas a pleno sol sob eCa apresentaram maiores valores de g s em paralelo a aumentos na densidade e no índice estomático, além dos maiores valores de A, V cmax e velocidade máxima de carboxilação limitada pela taxa de transporte de elétrons, bem como maior acúmulo de biomassa. Mesmo quando essas plantas foram analisadas sob baixa irradiância, não mostraram grande redução de g s , o que poderia ajudar no maior ganho de biomassa dessas plantas ao longo do tempo. Tanto a maior disponibilidade de luz como de CO 2 impactou positivamente o ganho de biomassa (e A), com efeitos interativos entre esses dois fatores. Sob eC a , o maior crescimento foi primordialmente governado por aspectos morfológicos à sombra (e.g. área foliar total), e fisiológicos ao sol (e.g. A). O sombreamento ora imposto permitiu uma exacerbação da plasticidade fenotípica à luz, sendo o CO 2 um importante fator no processo de manifestação dessa plasticidade. Coletivamente, os resultados oferecem novas informações sobre os efeitos positivos de eC a sobre o desempenho fotossintético e crescimento do cafeeiro, seja a pleno sol ou sob condições de baixa disponibilidade lumínica. Palavras-chave: Coffea arabica. Estômato. Fotossíntese. Luz. Mudanças Climáticas. Plasticidade Fenotípica. Sombreamento.Item Nickel and glyphosate on the potentiation of the soybean resistance against infection by Phakopsora pachyrhizi(Universidade Federal de Viçosa, 2020-03-18) Einhardt, Andersom Milech; Rodrigues, Fabrício de Ávila; http://lattes.cnpq.br/8666942935119852In this study, the effects of nickel (Ni) (60 g ha -1 Ni) and glyphosate (Gl) (960 g ha -1 e.a. Gl) spray on the antioxidative, defense, and ethylene metabolisms of soybean plants inoculated with P. pachyrhizi were evaluated. In the first experiment, the severity of Asian soybean rust (ASR) decreased by 35% in plants of cv. TMG 135 treated with Ni (+Ni). The malondialdehyde (MDA) concentration was higher in plants not treated with Ni (-Ni) than in +Ni plants and was linked to ASR severity and extensive colonization of the palisade and spongy parenchyma cells by fungal hyphae. The lignin concentration, β-1,3-glucanase (GLU) activity, and expression of the URE gene and the defense-related genes PAL1.1, PAL2.1, CHI1B1, and PR-1A were up- regulated in +Ni infected plants. Taken together, the information provided in this study showed the great potential of Ni to increase the basal level of soybean resistance to ASR and to complement other control methods within the context of sustainable agriculture. In the second experiment, ASR severity in plants of cv. TMG 135 decreased by 34% due to Ni supply. In inoculated plants, the MDA concentration and superoxide (O2-) and hydrogen peroxide (H2O2) accumulation were lower for +Ni plants in comparison to -Ni plants. The antioxidant enzymes activities were inefficient to avoid the high reactive species of oxygen (ROS) accumulation on -Ni inoculated plants. The photosynthetic pigments, maximum photochemical efficiency of photosystem II (PSII), effective yield of PSII, electron transport rate, rate of net carbon assimilation, stomatal conductance to water vapor, and transpiration rate values were higher and the yield for other non-regulated losses and internal CO2 concentration values were lower for +Ni inoculated plants in comparison to -Ni inoculated plants. High ROS production and the great damage to the photosynthetic apparatus damage caused by P. pachyrhizi infection on -Ni plants affected the synthesis of the sugars and increased the energetic consumption limiting therefore, the plant energetic reserves faster in contrast to +Ni plants. In conclusion, the cellular oxidative damage and the impairment on the photosynthetic apparatus of soybean plants caused by P. pachyrhizi infection were alleviated by supplying Ni foliarly. In the thirst experiment, ASR severity was lower by 37, 68, and 77% in plants of cv. TMG 132 supplied with Ni, Gl, and Ni and Gl (Ni+Gl) in comparison to plants supplied with water (control). The inoculation caused largest and fastest increase in the concentration of ROS and MDA in control plants in comparison to Ni and Gl plants. In inoculated plants, the Ni and Gl increased phenylalanine ammonia lyase and GLU activities and phenolics concentration. Additionally, Ni-treated plants showed a fasted cell wall lignification than control plants. Polyphenoloxidase activity was increased by Gl at 5 days after inoculation, regardless of P. pachyrhizi infection. In conclusion, this study demonstrated that Ni and Gl regulate differently the activity of defense enzymes and did not affect the antioxidant enzymes in soybean plants infected by P. pachyrhizi. In the fourth experiment, the ASR severity was reduced on plants of cv. TMG 132 sprayed with Ni and Gl. Carotenoids and chlorophylls concentrations were preserved for Ni, Gl, and Ni+Gl inoculated plants in comparison to that in control plants. Parameters of chlorophyll a fluorescence revealed photosynthetic apparatus damage and lowest destination of energy to photochemistry process on inoculated plants from the control treatment. Limitations on the photosynthetic machinery capacity of inoculated plants to capture light and use the absorbed energy by PSII reflected on their capacity to reduce the CO2 as indicated by the high values for internal CO2 concentration and low values for rate of net carbon assimilation. Low sugars concentration on inoculated plants from the control treatment was linked to their reduced photosynthetic capacity due to the high ASR severity. For non-inoculated plants, ethylene concentration was not affected by Ni and Gl, but its concentration decreased for inoculated plants being more pronounced for plants from the control treatment. In conclusion, this study sheds light into the role played by both Ni and Gl on ASR control from a physiological point of view. Soybean plants exposed to Ni and Gl were able to maintain their photosynthetic capacity and the great ethylene concentration during the infection process of P. pachyrhizi. Keywords: Plant nutrition. Herbicide. Host defense. Photosynthesis. Asian Soybean Rust.Item Introdução de características do mecanismo fotossintético C4 em espécies C3 da família Cleomaceae(Universidade Federal de Viçosa, 2021-07-16) Gomes, Priscilla Falquetto; Nesi, Adriano Nunes; http://lattes.cnpq.br/9787066085481887Cleomaceae é uma família de plantas interessante para estudos de evolução do mecanismo fotossintético C4 , uma vez que contém representantes dos três mecanismos (C3, C4 e C3 -C4 ). O mecanismo fotossintético C4 evoluiu independentemente da fotossíntese C3 . Para estabelecimento do mecanismo C4 ocorreram adaptações morfofisiológicas nas plantas, tais como a diferenciação de células da bainha do feixe vascular, alterações da maquinaria enzimática e aumento do transporte de metabólitos, gerando um mecanismo com maior eficiência fotossintética. Neste trabalho foram gerados híbridos interespecíficos entre duas espécies C3 (T. hassleriana e T. longicarpa) e uma espécie C4 (G. gynandra), ambas da família Cleomaceae., a fim de promover interações genômicas que resultam em fenótipos distintos dos observados nos parentais em relação ao mecanismo fotossintético. Os híbridos e parentais foram avaliados em termos de características anatômicas, bioquímicas e fisiológicas. As linhas híbridas obtidas entre o cruzamento de T. longicarpa e G. gynandra apresentaram anatomia proto-Kranz, caracterizadas por aumento na largura das células da bainha do feixe vascular, aumento na densidade de venação, e redução na distância internerval, além de apresentarem redução de aproximadamente 20% no ponto de compensação de CO2 em relação a T. longicarpa. O perfil metabólico em folhas dessas mesmas linhas híbridas apresentou mínimas diferenças, porém capazes de diferenciar híbridos e parentais em uma análise de componentes principais. Em termos de viabilidade de sementes verificou-se que os cruzamentos entre T. longicarpa e G. gynandra produziram sementes viáveis e descendentes férteis, apresentando potencial para seguir com estudos na população F2. Portanto, os resultados obtidos demonstram o potencial da hibridação interespecífica utilizando espécies da família Cleomaceae em oferecer novas perspectivas para estudos de mecanismos concentradores de CO2 em plantas. Palavras-chave: Cleomaceae. Hibridação interespecífica. Mecanismos concentradores de CO2 . Metabolismo.Item Photoperiod, salinity, and elicitors modulate the growth, morphophysiology, and biosynthesis of 20-hydroxyecdysone in Pfaffia glomerata (Spreng.) Pedersen(Universidade Federal de Viçosa, 2021-03-01) Fortini, Evandro Alexandre; Otoni, Wagner Campos; http://lattes.cnpq.br/8696085559149421Pfaffia glomerata is a plant widely used in traditional medicine, and a major producer of the secondary metabolite 20-hydroxyecdysone (20-E). Studies indicate that the biosynthesis of 20- E in P. glomerata can be regulated by abiotic stresses, but the mechanisms involved in this regulation are still unclear. Aiming to understand the physiological and molecular basis involved in the regulation of 20-E biosynthesis in P. glomerata, as affected by abiotic factors, ploidy level, and elicitation, three experiments were conducted. In the first experiment, plants of P. glomerata (accessions 22 and 43) were grown in vitro for 40 days under 4 different daily photoperiods: 4, 8, 16, and 24 h of light. We found that plants exhibited higher photosynthesis and biomass accumulation when grown in longer photoperiods. The plants also had anatomical and primary metabolism changes in response to the photoperiods tested, and the magnitude of these changes was accession-dependent. Furthermore, longer photoperiods promoted an increase in 20-E production, possibly as a result of higher carbon availability in the plants. In the second experiment, P. glomerata plants were grown in vitro and subjected to the following treatments: NaCl (50 mM), 5-azacytidine (5-azaC, 25 μM), and NaCl+5-azaC. After 40 days, we observed that the treatments promoted a significant reduction in growth and photosynthesis, as well as an increase in reactive oxygen species (ROS) and antioxidant enzyme production and an adjustment in primary metabolism. Through proteomic analyses, we identified differentially accumulated proteins mainly associated with the metabolism of carbohydrates, amino acids, and secondary metabolites, which may help us understand the salt stress and 5-azaC tolerance responses compared to control. Besides, we found that the 5-azaC and NaCl+5-azaC treatments reduced the accumulation of jasmonate biosynthesis-related protein, and this may contribute to reduced 20-E signaling and biosynthesis. In the third experiment, two different ploidies of P. glomerata (A22, diploid; and P28, a tetraploid derived from A22) were grown in vitro for 40 days, and the plants were elicited in the first 20 days with methyl jasmonate (methyl-JA) and methyl salicylate (methyl-SA). The elicitors induced contrasting anatomical modifications in P. glomerata leaves. Elicitation also reduced the photosynthetic rate of the plants, with a consequent change in primary metabolite content and reduction in growth. Treatments with methyl-JA and methyl-SA promoted oxidative stress, but also ROS mitigation by increasingantioxidant enzymes, and these changes were more significant in diploid plants. The production of 20-E was stimulated by elicitation with methyl-JA and was also higher in tetraploid plants. On the other hand, methyl-SA down-regulates Phantom gene expression, with a consequent reduction in 20-E biosynthesis. Taken together, our data provide important information on molecular, biochemical, and physiological mechanisms involved with the regulation of 20-E biosynthesis, as well as enable biotechnological strategies for increasing the production of this metabolite in P. glomerata plants grown in vitro. Keywords: Phytoecdysteroids. Abiotic stress. Photosynthesis. Medicinal plant. Proteomics. Phytohormones. Polyploidy.Item Ethylene and nickel in the resistance of maize against the infection by Exserohilum turcicum(Universidade Federal de Viçosa, 2020-11-27) Oliveira, Lillian Matias de; Rodrigues, Fabrício Ávila; http://lattes.cnpq.br/0139096690634343Diseases cause a negative impact on maize yield worldwide, and the northern leaf blight (NLB), caused by the hemibiotrophic fungus Exserohilum turcicum, is one of the most important. Considering the harmful effects of E. turcicum infection in the leaves of maize plants, the objectives of this study were to investigate the alterations in the photosynthesis (parameters related to leaf gas exchange and chlorophyll a fluorescence), the foliar concentration of micronutrients, and reactive oxygen species (ROS), production of ethylene, activities of both defense and antioxidant enzymes, and the expression of the genes related to the production of hormones. The first study investigated the role of ethylene (ET) in increasing the resistance of maize plants against NLB at physiological, biochemical, and molecular levels. Maize plants were sprayed with ET, aminooxyacetic acid (AOA) (an ET inhibitor), and water (control). The ET application increased its concentration in the leaf tissues and contributed to the expansion of NLB lesions. Also, high NLB severity resulted in lower values for net carbon assimilation rate, stomatal conductance, transpiration rate, and maximum quantum yield of photosystem II (F v/F m) at advanced stages of fungal infection. Lower concentration of pigments and higher concentrations of malonaldehyde (MDA) and hydrogen peroxide (H2O2) were noticed for ET- sprayed plants infected by E. turcicum. Great NLB development in the leaves of ET-sprayed plants can probably be attributed to the lower activities of antioxidative (ascorbate peroxidase, glutathione reductase, and superoxide dismutase) and defense (chitinase, β-1,3-glucanase, lipoxygenase, and phenylalanine ammonia-lyase) enzymes. The second study was carried out to investigate the effect of foliar nickel (Ni) spray on the potentiation of maize resistance against E. turcicum infection by examining alterations at biochemical and physiological levels. In the in vitro assay, Ni efficiently inhibited the mycelial growth of E. turcicum. For Ni-sprayed and inoculated plants, there were higher foliar concentrations of manganese and Ni. These plants exhibited significant decreases of 33 and 24%, respectively, for NLB severity at 12 and 16 days after inoculation. There were lower MDA and H2O2 concentrations in the leaves of +Ni inoculated plants. The decrease in NLB severity for Ni-sprayed plants was related to its direct effect against E. turcicum infection or through the potentiation of host defense responses such as high lipoxygenase and polyphenoloxidase activities as well as great production of phenolics and lignin. Keywords: Antioxidative metabolism. Host defense responses. Northern leaf blight. Plant nutrition. Plant hormone. Photosynthesis.Item Effects of salt stress on growth and metabolism of tomato (Solanum lycopersicum L.) plants associated with high concentration of carbon dioxide(Universidade Federal de Viçosa, 2020-11-06) Brito, Fred Augusto Lourêdo de; Ribeiro, Dimas MendesSoil salinity is an important environmental factor that limits the crop yield. On the other hand, the elevated CO2 concentration (e[CO2]) is able to mitigate the negative effects of salt stress on crop yield by stimulating photosynthetic rate in many C3 species, including Solanum lycopersicum. However, the impact of soil salinization on the relationship between biomass allocation, hormone biosynthesis and the primary metabolism of tomato plants under e[CO2] are hitherto not well understood. In this context, tomato plants grown under salt stress showed high Na+ concentration in tissues under both ambient [CO2] (a[CO2]) and e[CO2]. Under a[CO2], plants treated with NaCl showed lower accumulation of biomass compared to untreated plants. However, e[CO2] restored the growth of tomato plants under saline stress by reducing concentration of abscisic acid (ABA) and the ethylene precursor 1-aminocyclopropane-1- carboxylic acid in leaves and roots. In addition, plants treated with NaCl under a[CO2] showed reduction of the concentration of Krebs Cycle intermediates and increase of amino acids glycine and serine, while the plants under e[CO2] treated with NaCl presented the recovery of these parameters to the levels of the control plants. These findings led to a new questioning whether plants with alterations in ABA biosynthesis present differential strategies of tolerance to saline stress under e[CO2]. Thus, we analyzed tomato plants cv. Micro-Tom (MT), ABA-deficient mutant notabilis (not) and plants with high ABA concentration (NCED) submitted to salt stress. The growth of not plants was more affected in relation to MT and NCED plants, mainly under conditions of salt stress under both [CO2]. On the other hand, e[CO2] led to increases in total biomass and leaf area for all genotypes under saline stress, compared to a[CO2]. In addition, NCED mutants showed greater growth in relation to the MT and not genotypes under e[CO2] in control and saline conditions. e[CO2] caused an increase in photosynthesis and reduction of photorespiration in the MT, not and NCED treated with NaCl compared to a[CO2]. In addition, e[CO2] induced changes in the primary metabolism which were associated with increases in dark respiration, especially of MT and not genotypes under saline stress. Taken together, our results suggest that e[CO2] alleviates the effects of saline stress on plants through increased photosynthesis, reduced photorespiration and reprogrammed primary metabolism by mechanisms independent of ABA concentration. Keywords: Photosynthesis. Respiration. Primary metabolism. Hormonal regulation. Salt stress. Tomato plant